Field of the Invention
The present invention relates to a method for producing an L-amino acid such as L-glutamic acid by fermentation using a bacterium. L-Amino acids are industrially useful as raw materials of seasonings and so forth.
Brief Description of the Related Art
L-Amino acids are industrially produced by, for example, fermentation using microorganisms such as bacteria having an L-amino acid-producing ability (Akashi, K. et al., Amino Acid Fermentation. Japan Scientific Societies Press, p. 195 to 215, 1986). For example, bacterial strains isolated from nature, or mutant strains thereof have been used. Also, the ability of microorganisms to produce L-amino acids can be improved by using recombinant DNA techniques. For example, the ability of bacteria to produce L-glutamic acid has been enhanced by increasing the phosphoketolase activity (WO2006/016705) or utilizing a mutant yggB gene (WO2006/070944).
Various C4-dicarboxylic acid-uptake carriers have been found in bacteria. Bacteria can uptake and metabolize C4-dicarboxylic acids via C4-dicarboxylic acid-uptake carriers. For example, it is known that the proteins encoded by the dctA gene, dcuA gene, and dcuB gene all have uptake ability for a C4-dicarboxylic acid such as aspartic acid (Karinou E. et al., The Escherichia coli SLC26 homologue YchM (DauA) is a C4-dicarboxylic acid transporter. Mol Microbiol. 2013 February; 87(3):623-40 and Janausch I G. et al., C4-dicarboxylate carriers and sensors in bacteria. Biochim Biophys Acta. 2002 January 17; 1553(1-2):39-56). It is also known that a protein encoded by dctA gene also has uptake ability for L-glutamic acid (Youn et al., Characterization of the Dicarboxylate Transporter DctA in Corynebacterium glutamicum. Journal Of Bacteriology. 2009 September 5480-5488).
In addition, a method for producing an L-amino acid using a coryneform bacterium having an increased expression of dctA gene has been reported (US2002-0106759), and includes an example in which L-lysine was produced with this bacterium. While L-amino acids other than L-lysine, such as L-glutamic acid, are also exemplified, it has not been reported whether other L-amino acids, such as L-glutamic acid, can be produced using this bacterium.
In addition, it is known that a protein encoded by the yggB gene has excretion ability for L-glutamic acid (WO2006/070944 and Nakamura et al., Mutations of the Corynebacterium glutamicum NCgl1221 Gene, Encoding a Mechanosensitive Channel Homolog, Induce 1-Glutamic Acid Production. Applied And Environmental Microbiology. 2007 July 4491-4498).